Trích dẫn APA

Sagan, C. (1997). Billions and billions: Thoughts on life and death at the brink of the millennium. Headline Book Publishing.

Trích dẫn kiểu Chicago

Sagan, Carl. Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium. London: Headline Book Publishing, 1997.

Trích dẫn MLA

Sagan, Carl. Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium. Headline Book Publishing, 1997.

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